During the in situ breaking down of bitumen from oil sand by means of steam and horizontal bore holes by means of the SAGD (Steam Assisted Gravity Drainage) method, large quantities of water vapor are required to heat the bitumen. Steam at a temperature of 250° C. with a quality of 0.95, i.e. almost superheated, is typically used. Although this steam has a high energy content, very large quantities of water accumulate and are extracted with the oil back to the surface and have to be processed there with significant outlay.
When using steam, the use of horizontal injection pipes longer than 1000 m is no longer practical due to the resulting pressure loss, which is known to be a function of the pipe length.
A SAGD method for extracting very heavy oil is known from U.S. Pat. No. 6,257,334 B1, in which, in addition to a so-called well pair consisting of pipes one on top of the other, further elements are also present, which are intended to improve the heating of the region. Also a facility for the electrical heating of certain regions is known from WO 03/054351 A1, with which a field is generated between two electrodes, heating the region in between them.
A method for the heavy oil deposit is also known from US 2006/015166 A1, in which a tool with electrodes is provided for the three-phase resistive heating of the deposit to reduce the viscosity of the heavy oil.